Perpendicular magnetic recording disk and manufacturing method thereof

1. A perpendicular magnetic recording disk for use in perpendicular magnetic recording, said perpendicular magnetic recording disk: comprising: a base; an underlayer formed over said base for controlling a crystal orientation of an upper layer; a nonmagnetic granular layer of a granular structure formed on said underlayer; and a magnetic recording layer comprising a ferromagnetic layer of a granular structure formed on said nonmagnetic granular layer; wherein said nonmagnetic granular layer comprises: an inorganic oxide matrix; and nonmagnetic metal crystal grains which are dispersed in said matrix of said nonmagnetic granular layer and which have a crystal orientation directed in a predetermined orientation that depends on a crystal orientation of said underlayer; and said ferromagnetic layer comprises: an inorganic oxide matrix; and magnetic crystal grains which are dispersed in said matrix of said ferromagnetic layer and which have an easy magnetization axis directed in a predetermined orientation that depends on the crystal orientation of said metal crystal grains; wherein the nonmagnetic metal crystal grains of the nonmagnetic granular layer include at least one metal element comprising at least Co or Cr included in the magnetic crystal grains in the ferromagnetic layer; wherein the magnetic recording layer further comprises: a magnetic coupling control layer on the ferromagnetic layer; and an exchange energy control layer which is formed on the magnetic coupling control layer and differs in composition from said ferromagnetic layer; wherein the magnetic coupling control layer controls magnetic coupling between the ferromagnetic layer and the exchange energy control layer and aligns an easy magnetization axis of the ferromagnetic layer and the exchange energy control layer; and wherein the magnetic coupling control layer is formed by Pd or Pt and the exchange energy control layer is formed by a multilayer composed of alternate-layered films.

2. A perpendicular magnetic recording disk as claimed in claim 1 , wherein the at least one metal element includes either cobalt or chromium.

3. A perpendicular magnetic recording disk as claimed in claim 1 , wherein the at least one metal element includes both cobalt and chromium.

4. A perpendicular magnetic recording disk as claimed in claim 1 , wherein the underlayer includes ruthenium.

5. A perpendicular magnetic recording disk for use in perpendicular magnetic recording, said perpendicular magnetic recording disk: comprising: a base; an underlayer of ruthenium formed over said base for controlling a crystal orientation of an upper layer; a nonmagnetic granular layer of a granular structure formed on said underlayer of ruthenium; and a magnetic recording layer comprising a ferromagnetic layer of a granular structure formed on said nonmagnetic granular layer; wherein said nonmagnetic granular layer comprises: an inorganic oxide matrix; and nonmagnetic metal crystal grains which are dispersed in said matrix of said nonmagnetic granular layer and which have a crystal orientation directed in a predetermined orientation that depends on a crystal orientation of said underlayer; and said ferromagnetic layer comprises: an inorganic oxide matrix; and magnetic crystal grains which are dispersed in said matrix of said ferromagnetic layer and which have an easy magnetization axis directed in a predetermined orientation that depends on the crystal orientation of said metal crystal grains; wherein the magnetic recording layer further comprises: a magnetic coupling control layer on the ferromagnetic layer; and an exchange energy control layer which is formed on the magnetic coupling control layer and differs in composition from said ferromagnetic layer; wherein said exchange energy control layer is a multi-layer film composed of alternate layer films where the entire multi-layer film has a thickness in the range of 1 nm to less than 5 nm; and wherein the magnetic coupling control layer controls magnetic coupling between the ferromagnetic layer and the exchange energy control layer and aligns an easy magnetization axis of the ferromagnetic layer and the exchange energy control layer.

6. A perpendicular magnetic recording disk as claimed in claim 5 , wherein the nonmagnetic metal crystal grains of the nonmagnetic granular layer include at least one metal element comprising at least Co or Cr included in the magnetic crystal grains in the ferromagnetic layer.

7. A perpendicular magnetic recording disk for use in perpendicular magnetic recording, said perpendicular magnetic recording disk: comprising: a base; an underlayer of ruthenium formed over said base for controlling a crystal orientation of an upper layer; a nonmagnetic granular layer of a granular structure formed on said underlayer of ruthenium; and a magnetic recording layer comprising a ferromagnetic layer of a granular structure formed on said nonmagnetic granular layer; wherein said nonmagnetic granular layer comprises: an inorganic oxide matrix; and nonmagnetic metal crystal grains which are dispersed in said matrix of said nonmagnetic granular layer and which have a crystal orientation directed in a predetermined orientation that depends on a crystal orientation of said underlayer; and said ferromagnetic layer comprises: an inorganic oxide matrix; and magnetic crystal grains which are dispersed in said matrix of said ferromagnetic layer and which have an easy magnetization axis directed in a predetermined orientation that depends on the crystal orientation of said metal crystal grains; wherein the magnetic recording layer further comprises: a magnetic coupling control layer on the ferromagnetic layer; and an exchange energy control layer which is formed on the magnetic coupling control layer, wherein the magnetic coupling control layer controls magnetic coupling between the ferromagnetic layer and the exchange energy control layer and aligns an easy magnetization axis of the ferromagnetic layer and the exchange energy control layer, wherein said nonmagnetic granular layer is formed by a nonmagnetic layer of Co, Cr, and Si 0 2 while the ferromagnetic layer contains CoCrPt crystal grains and has a granular structure formed by Co, Cr, Pt, and SiO 2 , and wherein the magnetic coupling control layer is formed by Pd or Pt while the exchange energy control layer is formed by a multilayer composed of alternate-layered films.

8. A perpendicular magnetic recording disk as claimed in claim 7 , wherein the alternate-layered films of the exchange energy control layer include a layer of a cobalt or its alloy and a layer of palladium or platinum.

9. A perpendicular magnetic recording disk for use in perpendicular magnetic recording, said perpendicular magnetic recording disk: comprising: a base; an underlayer formed over said base for controlling a crystal orientation of an upper layer; a nonmagnetic granular layer of a granular structure formed on said underlayer; and a magnetic recording layer comprising a ferromagnetic layer of a granular structure formed on said nonmagnetic granular layer; wherein said nonmagnetic granular layer comprises: an inorganic oxide matrix; and nonmagnetic metal crystal grains which are dispersed in said matrix of said nonmagnetic granular layer and which have a crystal orientation directed in a predetermined orientation that depends on a crystal orientation of said underlayer; and said ferromagnetic layer comprises: an inorganic oxide matrix; and magnetic crystal grains which are dispersed in said matrix of said ferromagnetic layer and which have an easy magnetization axis directed in a predetermined orientation that depends on the crystal orientation of said metal crystal grains; wherein the nonmagnetic metal crystal grains of the nonmagnetic granular layer include at least one metal element comprising at least Co or Cr included in the magnetic crystal grains in the ferromagnetic layer; wherein the magnetic recording layer further comprises: a magnetic coupling control layer on the ferromagnetic layer; and an exchange energy control layer which is formed on the magnetic coupling control layer and differs in composition from said ferromagnetic layer; wherein the magnetic coupling control layer controls magnetic coupling between the ferromagnetic layer and the exchange energy control layer and aligns an easy magnetization axis of the ferromagnetic layer and the exchange energy control layer, wherein said exchange energy control layer comprises multiple films that are alternately layered.

10. A perpendicular magnetic recording disk as claimed in claim 1 , wherein said exchange energy control layer has a thickness in the range of 1 nm to less than 5 nm.

11. A perpendicular magnetic recording disk as claimed in claim 1 , wherein said exchange energy control layer comprises (1) alternate layered films of cobalt or an alloy thereof and palladium or (2) alternately layered films of cobalt or an alloy thereof and platinum.

12. A perpendicular magnetic recording disk for use in perpendicular magnetic recording, said perpendicular magnetic recording disk: comprising: a base; an underlayer of ruthenium formed over said base for controlling a crystal orientation of an upper layer; a nonmagnetic granular layer of a granular structure formed on said underlayer of ruthenium; and a magnetic recording layer comprising a ferromagnetic layer of a granular structure formed on said nonmagnetic granular layer; wherein the combined thickness of the underlayer and the nonmagnetic granular layer is in the range of 150 Å-300 Å wherein said nonmagnetic granular layer comprises: an inorganic oxide matrix; and nonmagnetic metal crystal grains which are dispersed in said matrix of said nonmagnetic granular layer and which have a crystal orientation directed in a predetermined orientation that depends on a crystal orientation of said underlayer; and said ferromagnetic layer comprises: an inorganic oxide matrix; and magnetic crystal grains which are dispersed in said matrix of said ferromagnetic layer and which have an easy magnetization axis directed in a predetermined orientation that depends on the crystal orientation of said metal crystal grains; wherein the magnetic recording layer further comprises: a magnetic coupling control layer on the ferromagnetic layer; and an exchange energy control layer which is formed on the magnetic coupling control layer and differs in composition from said ferromagnetic layer; and wherein the magnetic coupling control layer controls magnetic coupling between the ferromagnetic layer and the exchange energy control layer and aligns an easy magnetization axis of the ferromagnetic layer and the exchange energy control layer, wherein said exchange energy control layer comprises multiple films that are alternately layered.

13. A perpendicular magnetic recording disk as claimed in claim 5 , wherein said exchange energy control layer comprises (1) alternate layered films of cobalt or an alloy thereof and palladium or (2) alternately layered films of cobalt or an alloy thereof and platinum.